fix(cgg): default createUser name arg to null (#397)

Since version 0.5.0 of graphglgen args can be not just nullable but voidable. This more precise type introduced a type error with the existing template where a model expecting only nullable now received a voidable.

Author: Nuno Vieira

packages/graphqlgen-templates/typescript-yoga/src/generated/graphqlgen.ts

@@ -1,8 +1,7 @@
 // Code generated by github.com/prisma/graphqlgen, DO NOT EDIT.
 
 import { GraphQLResolveInfo } from 'graphql'
-import { Post, User } from '../types'
-import { Context } from '../types'
+import { Post, User, Context } from '../types'
 
 export namespace QueryResolvers {
   export const defaultResolvers = {}

packages/graphqlgen-templates/typescript-yoga/src/schema.graphql

@@ -5,7 +5,7 @@ type Query {
 }
 
 type Mutation {
-  createUser(name: String): User!
+  createUser(name: String = null): User!
   createDraft(title: String!, content: String!, authorId: ID!): Post!
   deletePost(id: ID!): Post
   publish(id: ID!): Post